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Help select suitable Mosfet for driving relay.

Discussion in 'Microcontrollers, Programming and IoT' started by HellasTechn, Apr 27, 2019.

  1. hevans1944

    hevans1944 Hop - AC8NS

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    That sounds like an excellent idea! I had forgotten about out discussion vis a vis the counterfeit MAXIM MAX232 back in 2016.

    Not to hijack this thread, but this topic of counterfeit Asian parts came up in the Flashlight thread when the OP purchased a counterfeit PICkit 3 programming pod for his PIC microprocessor. Fortunately, he was able to return it and get his money back, but who needs that kind of trouble? I have run into a similar problem with counterfeit RS-232-to-USB converters. These are legitimately made in Taiwan using a chip designed there, but counterfeits from mainland China abound. Some work, but later software drivers would "brick" those chips if the software "discovered" their use. When I purchased, about a year ago, a converter module (my laptop PC has no serial ports) I bought it from Amazon and have had no problems with it.
     
  2. Bluejets

    Bluejets

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    Yes, that was another story and if I remember that particular mob was forced to pull it's head in and issue a fix for it's deliberate actions.
     
  3. HellasTechn

    HellasTechn

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    Should i add a gate resistor to make sure that no current will go back to the microcontroller in case the mosfet fails ?
     
  4. Bluejets

    Bluejets

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    Oct 5, 2014
    You can, many do.

    However it's not to stop any current flow back into the micro.

    It is to limit the micro pin current.

    I think the usual value is around 120 ohm.
     
    HellasTechn likes this.
  5. Minder

    Minder

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  6. WHONOES

    WHONOES

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    MOSFETS are susceptible to parasitic oscillation. The is due to any pcb track or wire inductance that can cause a series resonant circuit in conjunction with the gate - source capacitance which can precipitate oscillation of the Fet. A resistor in series with the gate forms a low pass pole which should negate this effect.
     
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